Apparatus for pressure casting



April 14, 1953 A. E. HOLDER 2,634,468

' APPARATUS FOR PRESSURE CASTING Filed Oct. 16. 1948 2 SI-EETS-SHEET 1IN VEN TOR. ALFRED E2 .fion DEE 162244, 72a l m April 14, 1953 A. E.HOLDER I APPARATUS FOR PRESSURE CASTING 2 SHEETS-SHEET 2 Filed 001.. 16.1948 JNVENTOR. 141.5550 1 h 0L DEE A ala, 72mm 91234 Patented Apr. 14,1953 UNITED STATES ATENT OFFICE 3 Claims. 1

This invention relates to die casting and more particularly to diecasting machinery of the hydraulic pressure type.

In the manufacture of die casting, it is desirable to increase thedensity of the casting so as to eliminate the porous nature of the metalof which the casting is composed.

An object of the present invention, therefore, is to obtain a densecasting by applying pressure against the molten metal until theresistance reaches a predetermined'pressure, whereupon, a secondaryapplication or a booster pressure is automatically and immediatelyapplied before the metal has an opportunity to harden in any portionthereof. The invention consists of an apparatus by means of which thisprocedure may be carried out, either on a new machine or on existingmachines without necessitating extensive change in the constructionthereof.

Referring now to the drawings, Fig. l is a top plan view of a pressuredie casting machine embodying the present invention; Fig. 2 is ahorizontal section taken adjacent the right hand end of the machineshown in Fig. 1 but on a scale larger than that of Fig. 1, the plane ofthe section being indicated on the line 22 of Fig. 3; Figs. 3 and 4 aresections taken on planes indicated by the correspondingly numbered linesin Fig, 2, and Fig. 5 is a combined wiring and hydraulic system diagramfor illustrating the operation of the invention.

The die casting machine is shown in general at It] in Fig. l as havingan entrance port II for receiving molten metal, and as having a ram 12which is used for forcing the metal into the mold r members which areindicated in general at l3 and 14, respectively. The ram is shown asterminating in a piston l5 which is mounted for reciprocation within acylinder 6. An intake conduit 2| is adapted to deliver :a liquid, suchas oil, to the cylinder from a source of supply indicated as a pump 20in Fig. 5. The construction of the cylinder I6 is such that as thepiston is moving forwardly on the delivery stroke, the liquid in advanceof the piston is returning to the reservoir 22 (Fig. 5) through conduit23.

The foregoing construction is illustrative of a type of pressure diecasting machine which has heretofore been in general commercial use. Thepresent invention contemplates the provision of a system and apparatusby means of which the ram forces molten metal into the mold membersuntil the mold is filled, whereupon the resistance .of the metal tocompression causes a pressure to 'be built up within the cylinder [6.When the:

pressure reaches a predetermined amount, a booster device isautomatically brought into operation to increase the pressure upon theram before the metal has a chance to cool in any portion thereof.

The booster apparatus embodying the present invention is shown in Fig. 2as two cylinders 25 and 26 which are disposed in tandem relationship.

The cylinder 25 has a larger bore than that of the cylinder 26 and thebore of the cylinder 26 is a continuation of the bore in the cylinder25. A piston 2'! is mounted for reciprocation within the cylinder 25 andhas a rod or ram 3| projecting from one side thereof and extending intothe bore of the cylinder 2%. Suitable rings on the ram prevent thepassage of liquid between the two cylinders.

The cylinder 25 is a double acting cylinder with a conduit 28 connectedto one end thereof and a conduit 29 connected to the other end foreffecting reciprocation of the piston 21. The cylinder 26 is incommunication with the interior of the cylinder l6 through a conduit 30,so that the ram 3| may force liquid into the cylinder 5 during a portionof the forward stroke of the ram l2, and may draw liquid out of thecylinder l6 upon the retractile stroke of the ram I2.

Under the normal operation of the apparatus, liquid under pressure isforced into the cylinder l6 until the resistance to the forward movementof the ram [2 causes the liquid pressure on the pressure side of thepiston i5 to reach a predetermined amount. That portion of the cylinderon the pressure side of the piston is in communication with a pressureresponsive device 35 through a conduit 36. The device 35 is showndiagrammatically in Fig. 5 as an expansible element which when expandedis adapted to close a switch 31 and thereby to control an electriccircuit by means of which suitable valves will be operated in thehydraulic system. The valves function (a) to cut off the flow of liquidthrough the conduit 2! to the cylinder l5 and (b) to apply liquid underpressure through the conduit 28 to the piston 27 so as to force theliquid within the cylinder 26 into the cylinder l6 and thereby impart abooster pressure to the ram [2. The booster pressure will be inaccordance with the ratio of the cross-sectional area of the bores inthe cylinders 25 and 26,'respectively, and for practical purposes I havefound that a ratio of 4 to 1 will produce satisfactory results in thefinished castmg.

The hydraulic system for carrying out the present invention includes apump 20, as aforesaid,

which may be driven by an electric motor (not shown) and which may havea pressure relief valve 40 connected to the conduit M on the dischargeside of the pump so as to enable the pump to be kept in constantoperation. The pressure relief valve may be connected to the reservoir22 through a conduit 42. The conduit 4| is connected to a four-way valve45 which in turn is connected through a conduit 23 to one end of thecylinder l6, and to the other end of the cylinder 16 through conduit 46,valve 4! and conduit 2| respectively. The valve 45 may also be connectedto the reservoir 22 through conduit 48.

The pump 25 also serves to deliver liquid to the cylinder 2-5, suchconnections being diagrammatically shown in Fig. as including conduits4| and 49, the latter of which is connected to a valve 58. The valve inturn is connected to one end of the cylinder 25 through conduit 28 andto the other end of the cylinder through conduit 29. The valve also hasa conduit 5! extending therefrom and connecting it to the reservoir 22.

In Fig. 5, the valve 41 is shown as having a member 55 oscillatablymounted therein and provided with a passageway 56 which is intended toestablish communication between conduits 45 and El whenever the valveoperating arm 51 is in the position shown by the full line position. Thevalve is normally biased to the full line position by a spring 58 but isadapted to be shifted to the dotted line position 57A whenever thesolenoid coil 59 is energized. Similarly, the valve 50 has a valvemember 60 which is attached to a valve arm 6| that is biased to the fullline position of Fig. 5 by means of a spring 62. The valve member 50 isadapted to be moved to the broken line position 65A whenever thesolenoid coil 63 is energized.

The valve 45 is utilized for initiating the advancing movement of theram 12 and for initiating the retractile movement at the completion ofthe formation of the casting in the mold. Accordingly, the valve isshown as having a valve member it which is adapted to be actuated by amanually operable arm Tl for movement from the full line position to theposition shown by the broken lines HA. In the full line position theconnections are such that liquid flows from the pump it through conduitsi! and 23 to eiTect a retractile movement of the ram, but in the dottedline position i lA, the connections are such that liquid flows from thepump through the conduit 4|, valve 45, conduit 46, valve 41, and conduit2|, into the cylinder l6 so as to advance the ram and to deliver acharge of molten metal into the mold members. The movement of the arm Hfrom the full to the dotted line position also closes a switch,indicated in general at 80, which is in circuit with the switch 31.Normally, the switch 31 is open until the pressure within the cylinderit reaches a predetermined amount, at which time the pressure responsivedevice 35 closes the switch and thereby energizes the coils 59 and 53 soas to swing the arms 5! and SI respectively from the full to the dottedline positions of Fig. 5. At such time, the valve 41 is closed andliquid under pressure is delivered to the cylinder so as to force theram 3| along the cylinder 25 and thereby to impart a booster pressure tothe cylinder "5. The pressure remains on the booster device until suchtime as the operator opens the switch 80 by moving the arm from thedotted line position HA to the full-line position it; This automaticallydisconnects the circuit through the solenoid coils and allows the valvemembers 55 and 6!] to be returned to the full line positions, whereuponthe ram 12 and the booster ram 3| are automatically returned to thestarting position.

The electrical circuit illustrated in Fig. 5 includes a source ofsupply, indicated by the leads and 86, and a master switch indicated ingeneral at 87. When the switch 30 is closed, assuming that the switch8'! is also closed, current flows through conductor 88, switch 80,conductor 89, switch 37, conductor St to junction 9!, where the currentdivides, part flowing through the coil 59, and part flowing throughconductor 92 to the coil 63 and thence back through conductor 93 tojunction 94, from whence current flows through conductor 95 back to thesource lead 86.

An important advantage of the present invention is the fact that theapplication of the secoiidary or booster pressure occurs automatically,whenever the pressure in the primary cylinder it reaches a predeterminedamount. I have found, for example, when the source of fluid pressuresupply is about one thousand pounds per square inch, and when thepressure responsive device 35 is set to operate at about 900 lbs. persquare inch, and when the ratio of the areas of the bores in thecylinders 25 and 25 respectively is e to 1, that castings are producedwhich have a high, smooth finish and are substantially free fromobjections incident to the presence of voids, porous places, stricturesor cracks.

I claim:

1. In a die casting machine of the type described having a die mold, aplunger adapted to inject a charge of molten metal into said mold, ahydraulically operated shot piston adapted to actuate said plunger, ahydraulic cylinder rigidly associated with said mold and in which saidshot piston operates, a booster piston, a hydraulic cylinder connectedin communication with the shot cylinder and in which said booster pistonoperates, the booster piston including a rod having a cross-sectionalarea smaller than the crosssectional area of the booster piston, a pairof conduits interconnected respectively with said shot and boostercylinders, a valve in each conduit, a hydraulic pump interconnected withsuch conduits and operable to deliver fluid under pressure to saidcylinders through said conduits, and

means for simultaneously closing the valve in the conduit leading to theshot cylinder and opening the valve in the conduit leading to thebooster cylinder whereby after said shot piston is advanced to cause theplunger to inject molten metal into said mold, and after movement of theshot piston has been momentarily arrested by the filling of the mold,said booster piston is advanced to increase the pressure in the shotcylinder.

2. In a die casting machine of the class described having a die mold, aplunger adapted to inject a charge of molten metal into said mold, ahydraulically operated shot piston adapted to actuate said plunger, ahydraulic cylinder rigidly associated with said mold and in which saidshot piston operates, a booster piston, a hydraulic cylinder connectedin communication with said shot cylinder and in which said boosterpiston operates, a rod fixed to the booster piston and having a crosssectio'nal area smaller than that of the booster piston, a pair ofconduits interconnected respectively with said shot and boostercylinders, a valve in each of said conduits, a hydra'ulic pumpinterconnected with said conduits and operable to deliver fluid-underpressure to said cylinders through said conduits, whereby when the valvein the conduit leading to the shot cylinder is open, said shot piston isadvanced to cause said plunger to inject molten metal into said mold,and a pressure responsive device in communication with the shot cylinderand operable upon the attainment of a predetermined pressure of fluid inthe shot cylinder to close the valve in the conduit leading to the shotcylinder and to open the valve in the conduit leading to the boostercylinder, to direct the flow of fluid from said pump into the boostercylinder whereby the booster piston is advanced to increase the pressurein the shot cylinder after the shot piston has been momentarily arrestedby the filling of the mold.

3. In a die casting machine of the class described having a die mold, aplunger adapted to inject a charge of molten metal into said mold, ahydraulically operated shot piston adapted to actuate said plunger, ahydraulic cylinder rigidly associated with said mold and in which saidshot piston operates, a booster piston, a hydraulic cylinder connectedin communication with said shot cylinder and in which said boosterpiston operates, a rod fixed to the booster piston and having across-sectional area smaller than that of the booster piston, a pair ofconduits interconnected respectively with said shot and boostercylinders, a valve in each of said conduits, a hydraulic pumpinterconnected with said conduits and operable to deliver fluid underpressure to said cylinders through said conduits, whereby when the valvein the conduit leading to the shot cylinder is open, said shot piston isadvanced to cause said plunger to inject molten metal into said mold,pressure responsive means communicating with the shot cylinder, anelectric switch actuated by the pressure responsive means, a circuit forsaid switch, and electromagnetic means in said circuit for closing thevalve in the conduit leading to the shot cylinder and opening the valvein the conduit leading to the booster cylinder to direct the flow offluid from said pump into the booster cylinder, whereby the boosterpiston is advanced to increase the pressure in the shot cylinder afterthe shot piston has been momentarily arrested by the filling of themold.

ALFRED EMIL HOLDER.

References Cited in the file of this patent UNITED STATES PATENTS-Number Name Date 1,781,168 Dollin et a1 Nov. 11, 1930 1,940,063 ShermanDec. 19, 1933 2,112,342 Lester et al Mar. 29, 1938 2,145,956 Stern Feb.'7, 1939 2,181,157 Smith Nov. 28, 1939 2,182,059 Schwartz Dec. 5, 19392,210,544 Galloway Aug. 6, 1940 2,214,308 Polak Sept. 10, 1940 2,365,282Lester et al. Dec. 17, 1944

